Automatic starter switch for the ignition and operation of fluorescent lamps



May 10, 1960 F. KNOBEL 2,936,403

AUTOMATIC STARTER SWITCH FOR THE IGNITION AND OPERATION OF FLUORESCENTLAMPS Filed July 17, 1958 15 ummillll ll llllIfllllillllllllll UnitedStates Patent "ice AUTOMATIC STARTER SWITCH FOR THE ,IGNI- TION ANDOPERATION OF FLUORESCENT LAMPS This invention relates to automaticstarter switches for the ignition and operation of fluorescent lampshaving at least one heated cathode.

Automatic starter switches are used for igniting fluorescent lampshaving heated cathodes and have the function, to automatically raiseupon manually switching on the light switch, the temperature of thecathodes to the optimum temperature, and to produce a sufficiently highinduction voltage for ignition of the lamp upon interruption of theignition circuit in combination with a choke connected in series-withthe lamp.

The most common starter switch of this kind is the so-called glowdischarge starter which is provided with normally open bimetal contactswhich, when heated by a glow discharge, close after a period which isnot accurately timed, and then open again. With short lamps it may occurthat they are ignited when the power switch is turned on and before thestarter contacts are closed. These so-called cold starts with unheatedcathodes are very harmful to the lamps and they considerably shorten thelife of said lamps. On the other hand, the glow discharge initiatingimmediately upon opening of the starter contacts causes an attenuationof induction peak voltages. This decreases the igniting reliability,especially when the ambient temperature is low. Further, after a certainoperating time, the changes in the igniting potential limit thetroublefree operation to some thousand operating hours. When the housingcontaining the glow discharge tube is made according to theinternational specification, the glow discharge starter occupies so muchspace that there remains not enough space to house a sufficiently ratedcondenser, i.e. a condenser according to specifications. The glowdischarge starter now in use does therefore not meet the internationalspecifications. Outside of these disadvantages the glow dischargestarter has the advantage of being extremely simple and cheap. This isthe reason why this starter in combination with a bayonet socket fittingthereto is in extensive use in illumination systems, despite of thedisadvantages mentioned before.

Other automatic starter switches known in the prior art comprise fourterminals and cannot be inserted to replace a starter switch in thesocket having two terminals.

Other starter switches known inthe prior art comprise a two-terminalsocket and a magnet relay which has a .very complicated and expensivedesign. This design often is subject to trouble. In most of the caseselectromagnetic operating starter switches have the disadvantage thatthey are not fully noiseless and that they aretoo sensitive to voltagechanges in the power line.

It is therefore an object of the invention to provide a save starterswitch with bimetal contacts fitting into a housing dimensionedaccording to the international specifications.

It is another object of the invention to provide a starter switch whichprevents cold starts which are detrimental to the life of the lamp. 7 7

It is another object of the invention to provide, a

2,936,403 Patented May 10, 1960 starterswitch operating independently ofthe ambient temperature.

It is another object of the invention to provide a starter switch havingan ignition condenser of suflicient size housed in a housing dimensionedaccording to international specifications.

It is another object of the invention to provide a starter switch withonly two terminals and which is exchangeable with glow discharge starterswitches.

A still further object of the invention is to provide a starter switchwhich can be adjusted without opening the housing.

Another object of the invention is to provide a starter switch whichrequires only a fraction of the space in a housing which is dimensionedaccording to international specifications.

. It is another object of this invention to provide a method foradjusting a starter switch.

' Objects and advantages other than those above set forth will beapparent from the following description when read in connection with theaccompanying drawing, in whichz' j Fig, 1 is a perspectivediagrammatical view of the starter switch,

Fig. 2 a fragmentary view of another embodiment of the invention,

Fig. 3 an electrical diagram for the embodiment of F Fig. 4 anelectrical diagram of antauxiliary power supply device, .and

.Fig. 5 a perspective fragmentary view of another embodiment.

From the power line 1, 2 the circuit leads over a power switch 3, achoke coil 4 and the cathodes 6, 7 of the fluorescent lamp 5 to theterminals 8, 9 of the connecting socket of the starter device. On thebase plate 19 two resiliently mounted bimetal strips 10 and 11 are soarranged that they co-operate with their normally closed contacts 12 andtheir normally open contacts 13. The deformation of these two bimetalsprings occurs in the same sense. In the temperature range from -20 C.to C. the deformation is of the same magnitude. Therefore, in the restposition of these contacts, the adjusted contact pressure remainsconstant within this temperature range. 7

The bimetal strip 10 which according to Fig. 1 is designed as alow ohmicresistor is at one point so closely surrounding the high ohmic resistor14, that heat from that resistor 14 will be easily transmitted to thebimetal strip 10. The high ohmic resistor is connected in series withthe condenser 15 to the two terminals 8, 9. An ignition condenser 16 andan attenuation resistor 17 is connected to the two terminals 8, 9parallel to the lamp 5. The condensers 15, 16 and the resistor 17 aremoulded into the housing by means of a plastic material. The housing 18is of the same size as one of a usual glow discharge starten This sizecorresponds to the international specifications. Due to the horizontaldisposition of the bimetal strips, only about one third of the space inthe housing 18 is required for the location of these strips, thecontacts and the heating resistors, even when the required spacings toprevent sneak currents are met; as can be easily seen from Fig. 1.Therefore, the remaining space will be large enough to locate there thecondensers 15, 16 and the resistor 17, these being of sufficient size toinsure perfect operation and to meet the prescribed specifications. Inconventional glow dis charge starters the glow discharge tube requiresso much space, that no sufiiciently large condenser can be placed intothe remaining space. These prior art glow discharge starters thereforedo not correspond to the international specifications. a

The described starter switch operates as follows:

Immediately upon switching-on the power switch 3 a heating current isflowing through the choke coil 4, the lamp cathode 6 to the terminal 8of the starter switch, which is electrically connected to one end of thebimetal strip 10 by means of a rivet, through the normally closedcontact 12, the rearward end of the bimetal strip 11 to the terminal 9,and from there through the other lamp cathode 7 back to the power line.The heating current heats the two lamp cathodes 6 and 7 and also thebimetal strip 10, which, in order to increase its electrical resistance,is considerably smaller than the bimetal strip 11. Due to the heat thebimetal strip 10 will bend upwardly. The normally closed contact 12 isopened and the voltage induced into the choke coil 4 ignites the arc inthe lamp 5, which is now used to keep the normally closed contact 12open, the high ohmic resistor 14 now providing the heating of themovable bimetal strip 10. This resistor could, in principle, beconnected parallel to the lamp 5, i.e. to the terminals 3 and 9. But inorder to avoid an attenuation of the induction voltage, and to increasethe reliability of ignition, especially when the ambient temperature islow, the resistor 14 shown in the diagram of Fig. l is not connecteddirectly parallel to the lamp 5, but by the intermediary of a condenser15. It is further important, that the thermal inertia of the high ohmicresistor 14 is very low so that the heating of this resistor 14 iseffective on the bimetal strip 10 before the contacts 12 close againafter being opened. The low thermal inertia of the high ohmic resistor14 offers the additional advantage, that upon opening the ignitionswitch, i.e.

switching-oh the lamp, this resistor cools off very quickly, and, sincethe thermal inertia of the bimetal strip 10 is also very small, theswitch elements return fast to their initial position and the starterswitch is quickly ready again for operation.

The low thermal inertia of the resistor 14 of the starter switch shownin the drawing is obtained, because the resistor 14 consists only of asmall mass weighing less than 0.1 gr., and because only a thin lacquerfilm provides the electrical insulation against the bimetal strip 10, sothat a good heat transfer, e.g. by convection, is provided between theresistor 14 and the bimetal strip 10.

It may, however, occur, that the lamp does not fire upon the firstopening of the contacts 12, when this opening occurs at an unfavorablemoment with respect to the momentary value of the current. Then, theresistor 14 will not be heated by the arc voltage of the lamp 5, but bythe considerably higher line voltage. In order to prevent this, anadditional normally open contact 13 is provided, which connects theterminals 8 and 9 as soon as the voltage on these terminals exceedsconsiderably the arc voltage of the lamp. At this moment the heatingcurrent is flowing from the terminal 8 through the normally open contact13, through the stationary bimetal strip 11 to the terminal 9. Theparallel resistor 14 no longer receives a voltage and cools off so thatthe contact 13 opens again and causes the firing of the lamp, whichfiring had failed before, when the normally open contact 12 broke thecircuit. The normally closed contact 12 is used only once for theignition, whereas the normally open contact 13 repeats the operation ofigniting until the lamp 5 is ignited. Because the lamp 5 is always firstshunted by the normally closed contact 12 when the power switch isturned on and because the heating current which is limited by the chokecoil 4 immediately heats up the two lamp cathodes 6 and 7, socalled coldstarts are completely avoided. Cold starts would be harmful to the lamp5 and reduce very considerably the life of it. The normally open contact13 which is connected to the movable bimetal strip is of courseelectrically insulated from that strip and connected .bya flexiblecopper wire 21 to the terminal 8. A condenser 16 in series with theattenuation. resistor 17 is preferably connected parallel to the lamp 5,i.e. between the terminals 8 and 9. This condenser 16 servesadditionally as a condenser to prevent radio interference and as anignition condenser, the condenser 15 being strongly attenuated in thisfunction by the high ohmic resistor 14. The resistor 17 serves only asattenuation resistor to prevent as well as possible the wear and thewelding together of the silver contacts 12 and 13. The effect providedby the condenser 16 to prevent radio interference can be substantiallyincreased, if instead 'of a simple choke coil 4, as shown in the diagramof Fig. l, a choke with two symmetric windings is used, as shown in Fig.3.

In an embodiment of an automatic starter switch according to Fig. l forthe ignition and operation of a common 40 watt fluorescent lamp ratedfor 0.42 amperes operating current and about volts arc voltage, partswith substantially the following technical data have been successfullyemployed:

Resistor 14: R==l5,000 S2 to 20,000 9 Dimensions: Diameter 0.039

Length 0.236 Weight: less than 0.1 gram. Condenser 15: Capacity C=0.l3,uF Condenser 16: Capacity C=0.02 F Resistor 17: R=5 to 10 S2 Bimetalstrip 10: 0.039"' 0.0047", weight: less than 0.05

gram Bimetal strip 11:-0.1l8l" 0.0047".

The condensers 15 and 16 and the resistor 17 were directly moulded witha plastic material into the upper part of the housing 18 having thedimensions Dia. 0.8268" 1.3386" In order to make the dimensioning of themovable bimetal strip independent from the heating current, which isparticularly of advantage for lamps of low wattage the heating of themovable bimetal strip can indirectly be effected by a helical heaterplaced near the stationary end of the bimetal strip 10. The helicalheater is heated by the current flowing through it. This possibility isshown in Figures 2 and 3. There the heating current is flowing from theterminal 8 over the low ohmic heating resistor 20 which also heats byheat radiation the bimetal strip 10 at the bent portion, so as to causethe normally closed contact to be opened. The other function is againexactly the same as in the embodiment described before which employsdirect heating for the bimetal strip 10.

The values of the heating resistors 14 and 20 and of the condenser 15can be adjusted for the different lamp wattages and types of lamps. Theheating-up time which is required for a certain type of lamp can beregulated within a wide range by adjusting the distance between theheating resistor and the bimetal strip 10. It is important that thestarter switch according to the invention enables to choose the thermalinertia of the switching system in such a way that this latter, independence of the ambient temperature, very closely corresponds to thatof the lamp cathodes 6 and 7, to thus make sure that the preheating ofthe lamp cathodes to the favorable temperature takes place before theignition and independently of the ambient temperature.

The combined function which consists in that the normally closed contactis opened with a delay depending on the heating current, and then iskept open in dependence of the arc voltage of the lamp, which isnegative to the lamp current and the line voltage, insures aconsiderable independence of the safe operation, even from relativelywide fluctuations of the line voltage.

In the embodiments of Figs. 1 and 2 the high ohmic resistor 14 is acommercial miniature carbon metallic resistor. As experiments haveproved, it is also possible to manufacture this resistor of asemi-conducting material so that the resistance will be dependent ontemperature or voltage, and to solder the resistor with the onemetallized end to the bimetal strip 10. Especially the type of resistoras it is .cornmerciallyxavailable from g Philips under the designationVDR, and which resistor consists of a voltagedependent material, couldbe employed in such manner that the deformation of the bimetal strip 10will be substantially constant within a large voltage range as it mayoccur under extremely bad line conditions.

The auxiliary power supply device shown in Fig. 4 serves for theadjusting of the starter switch when it is manufactured. Connected tothe power line 21 is a regulating transformer 22, the secondary voltageof which can be regulated at wish by moving a contact 23, whereby theadjusted voltage can be read from a volt meter 24. Connected into thesecondary circuit of the transformer 23 is a regulating resistor 25, anincandescent lamp 26 and an ammeter 27. The starter switch which can bedesigned as shown in Figures 2 and 3 is connected to the terminals 28,29 to be adjusted and tested. By adjusting the regulating resistor 25,the current in the ammeter 27 is adjusted so as to be equal to thesmallest possible preheating current of the fluorescent lamp for whichthe starter device is designated. For a 40 watt lamp as it is in commonuse and operating at 0.43 A. operating current and 103 v. rated arevoltage, this smallest possible preheating current is 0.38 A. Thevoltage on the volt meter 24 is further adjusted such that itcorresponds to the lowthis resistor 20 to the bimetal strip 10. In thisway, the

heat transfer caused by radiation is altered until the de- 1 sired delayin switching is obtained. When, after this delay in switching, thenormally closed contact 12 opens, the lowest possible arc voltage, asadjusted on the voltmeter 24, is applied to the starter switch. Withthis are voltage the normally closed contact must securely remain open.If this is not the case, it has to be accordingly adjusted by bendingthe bimetal strip 11. With the described auxiliary device it istherefore possible to adjust with one measuring the delay in switchingas well as the keeping open of the normally closed contacts at theoccurring lowest possible current and voltage values.

After the adjusting of the normally closed contact 12 a voltagecorresponding to maximum voltage of the respective type of lamp can beadjusted on the transformer 22 of the auxiliary device by moving thecontact 23. This test voltage is e.g. 130 v. for the usual 40 watt lamp.Now, the control is made to be sure that the normally open contact 13does not yet close at this voltage. Then a voltage is adjusted on thetransformer 22 which corresponds to the lowest permittable no-loadvoltage. This voltage is for a 40 watt lamp according to internationalspecifications e.g. 140 v. Now it can be checked that the normally opencontact closes securely at this voltage.

In the embodiment according to Fig. an adjusting screw 31, 32 screwedthrough the insulating base plate 19 is acting on every bimetal strip10, 11. By screwing in the screw 31 the contact pressure on the contact12 is increased, whereas this contact pressure is reduced when the screw32 is tightened. By screwing in the one or the other screw in thedirection of the arrows, the contact pressure accordingly can be varied.An adjusting screw could also act only on one of the two bimetal strips,whereby the contact pressure could also be increased or decreased bytightening or loosening the screw. Because the adjusting screws traversethe base plate 19, the contact pressure can be regulated without firstopening the housing.

I claim:

1. An automatic starter switch for the ignition and operation of afluorescent lamp comprising a housing including a connecting sockethaving a pair of terminals,

g a fluorescent lamp cathode heating circuit connecting said pair ofterminals, said circuit including a temperature sensitive means, a lowohmic resistor for heating the temperature sensitive means and anormally closed contact operated by said temperature sensitive means toopen when the temperature sensitive means is heated, a high ohmicheating resistor bridging said normally closed contact and adapted toheat the said temperature sensitive means and maintain said normallyclosed contact open when the fluorescent lamp is ignited, and a normallyopen contact bridging said pair of terminals and said cathode heatingcircuit and operated by the temperature sensitive means to close whenheated by said high ohmic resistor upon failure of the fluorescent lampto ignite, said high ohmic heating resistor having a low thermal inertiawhereby to exert a fast heating and cooling effect on said temperaturesensitive means.

2. An automatic starter switch for the ignition and operation of afluorescent lamp comprising a housing including a connecting sockethaving a pair of terminals, a fluorescent lamp cathode heating circuitconnecting said pair of terminals, said circuit including a temperaturesensitive means and a normally closed contact operated by saidtemperature sensitivemeans to open when the temperature sensitive meansis heated, a high ohmic heating resistor bridging said normally closedcontact and adapted to heat the said temperature sensitive means andmaintain said normally closed contact open when the fluorescent lamp isignited, and a normally open contact bridging said pair of terminals andsaid cathode heatingcircuit and insulated from but operated by thetemperature sensitive means to close when heated by said high ohmicresistor upon failure of the fluorescent lamp to ignite.

3. An automatic starter switch according to claim 1 wherein said highohmic heating resistor is located in intimate relation to saidtemperature sensitive means whereby heat is quickly transferred thereto.

4. An automatic starter switch according to claim 1 wherein saidtemperature sensitive means is horizontally positioned in said housingand together with said normally closed and open contacts and said lowand high ohmic resistors occupy only a small part of the vertical 1space available 'in said housing, and an ignition condenser ofrelatively large size positioned in the remaining vertical space andoccupying approximately all of the remaining space of said housing.

5, An automatic starter switch according to claim 1 wherein an ignitioncondenser and an attenuation resistor in series are additionallyprovided bridging said pair of terminals.

6. An automatic starter switch according to claim 1 wherein isadditionally provided a condenser connected in series with said highohmic heating resistor in bridg ing relation to said normally closedcontact.

7. An automatic starter switch according to claim 5 wherein saidignition condenser and said attenuation resistor together with anadditional condenser in series with said high ohmic resistor arepositioned in the upper part of said housing and molded therein by meansof plastic material.

8. An automatic starter switch according to claim 2 wherein saidtemperature sensitive means comprises a first and a second bimetallicstrip, said normally closed contact being operated to open by said firstbimetallic strip upon heating thereof, the movable part of said normallyopen contact being insulatedly carried by said first bimetallic stripand the stationary parts of both said normally closed and open contactsbeing carried by said second bimetallic strip, said bimetallic stripshaving the same deformation characteristics with respect to changes intemperature so that undue changes in contact pressure are avoided.

9. An automatic starter switch according to claim 1 wherein said highohmic heating resistor comprises a carbon metallic resistor providedwith a lacquer insulation and having a diameter of approximately 0.039inch and a length of approximately 0.236 inch.

10. An automatic starter switch according to claim 1 wherein said highohmic heating resistor comprises a voltage-dependent semiconductormaterial having a metallized surface which is soldered directly to saidtemperature sensitive means.

11. An automatic starter switch according to claim 1 wherein said highohmic heating resistor has a weight of less than 0.1 gram and ispositioned close to a portion of said temperature sensitive means, saidmeans having a weight of less than 0.05 gram whereby to obtain a lowthermal inertia and fast operation of said normally closed and opencontacts.

12. An automatic starter switch according to claim 1 wherein isadditionally provided a regulating means engaging said temperaturesensitive means and extending through said housing for adjusting fromthe outside thereof, said regulating means being adapted to adjust thecontact pressure of said normally closed and open contacts.

13. An automatic starter switch according to claim '8 wherein said firstand second bimetallic strips each have a U-shaped mounting end securedto an insulating portion of said housing, and an adjusting screw isthreaded through said insulating portion of the housing and bearsagainst the bight of the mounting end of one of said bimetallic strips.

14. A method of adjusting a fluorescent starter switch 30 open contactand a heating element adjacent thereto, comprising passing through theswitch the smallest possible preheating current for a fluorescent lampwith which the starter switch is to be used, measuring the delay timefor the switch to open, varying the distance between the heating elementand the heat responsive element until the desired delay time isattained, passing a voltage through the switch which is the lowestpossible arc voltage of the lamp when the normally closed contact isopen, determining whether this voltage will cause said contact to remainopen, varying the distance between the normally closed contact and acontact on the heat responsive element to a position where said voltagecauses said normally closed contact to remain open.

15. The method of claim 14 comprising passing a voltage through thestarter switch corresponding to the maximum arc voltage of the lamp,determining whether the normally open contact closes at this voltage,adjusting said contact to a position where it remains open at thisvoltage.

16. The method of claim 14 comprising passing a voltage through thestarter switch corresponding to the lowest permittable no-load voltagefor the lamp, determining whether the normally open contact closes atthis voltage, adjusting said normally open contact to a position whereit securely closes at this voltage.

McCarthy Aug. 10, 1943 Smith et al Aug. 8, 1944

